1. Field of the Invention
The invention relates to a polishing method and a polishing system. More particularly, the invention relates to a polishing system capable of providing better polishing uniformity on a surface of a polishing article and a polishing method of the same.
2. Description of Related Art
With the progress in the industry, the planarization process is often adopted for fabricating various devices. In the planarization process, the chemical mechanical polishing (CMP) process is often applied in the industry. Generally, the chemical mechanical polishing process is performed by supplying a slurry having chemical mixtures on a polishing pad, applying a pressure on the polishing article to be polished to press it on the polishing pad, and providing a relative motion between the polishing article and the polishing pad. Through the mechanical friction generated by the relative motion and the chemical effect of the polishing slurry, a portion of the surface of the planarization.
The conventional polishing pad includes a plurality of concentric circular grooves used to accommodate or remove residues or by-products generated from the polishing process, and enable a polishing article to be easily detached away from the circular polishing pad when the polishing process is completed. During the polishing process, not only does the polishing pad rotate, but the polishing article in contact with the surface of the polishing pad also rotates. However, as the concentric circular grooves on the conventional polishing pad are right circular grooves, and the polishing article rotates along an axis passing through the center point thereof as a rotational axis. Thus, when the direction between a particular point and the center point of the polishing article is perpendicular to the tangential direction of the grooves, the particular point will constantly contact a groove position or a non-groove position. For example, if the particular point contacts the groove position, points adjacent to the particular point would constantly contact the non-groove positions, thus affecting the polishing uniformity. Moreover, the above problem gets worse at positions closer to the central portion of the polishing article, as the central portion of the polishing article almost constantly contacts a specific position (for example, the groove position or the non-groove position) on the polishing pad during the whole polishing process. Therefore, the polishing rate of the central portion of the polishing article is lower or higher than the polishing rates of the other near portions, depending on whether the central portion constantly contacts the groove position or the non-groove position. The problem of non-uniform polishing rate of the polishing article may eventually degrade the reliability of the device.
Therefore, a polishing method and a polishing system are required to provide a better polishing uniformity.